1. Field of the Invention
The invention relates to a stabilization device for extending characteristic map of a compressor
2. Discussion of Background
Such stabilization devices are known for axial and radial compressors. In the use of turbo compressors, the aim is to achieve characteristics without hysteresis which fall monotonically with increasing through-flow, in order to achieve a high reliability in the case of operation under part load. Such continuous characteristics are denoted as stable. In the case of part load, however, stable characteristics are the more difficult to achieve the larger the pressure ratio at the design point. Consequently, an attempt is made to produce the desired characteristics by means of additional stabilization devices.
Patent EP 0,229,519 contains a description of a stabilization device for a radial compressor which device is distinguished by the fact that as a sheathing for the impeller the inner housing has radial bores or slots which produce a connection between the incoming-flow duct and the blading and in this case are more or less covered by the blades on the blade side. Although the pumping or stability limit is thereby displaced in the shape of the characteristic, the efficiency of the compressor is simultaneously sharply reduced.
Also known is a centrifugal compressor (U.S. Pat. No. 4,212,585) in which there is present a housing attachment with free recesses which extend in the flow direction. However, particularly in the part-load range these recesses produce a pumping effect, that is to say unstable characteristics. The stabilization device described in the Patent CH 675,279 likewise consists of a recess in the housing of the radial compressor, but in this case there is integrated into this recess a stabilization ring which is arranged upstream of the impeller and outside the main flow and bears on its outer circumference a number of blades which are anchored on the inner contour of the recess. The disadvantage of this solution is the complicated configuration of the housing and of the stabilization device.
It may be stated in summary that the known technical solutions for stabilizing the compressor characteristic map contain a special configuration of the compressor housing. A severe restriction of the compressor reorders possible a recirculation flow through the or in the openings arranged in the compressor housing.
The disadvantage of these known technical solutions is the complicated housing configuration. In addition, in the case of conventional radial impeller designs the runner blades are strongly loaded in the inlet region by vibrations which can be further amplified by the known stabilizers. Furthermore, the boundary layer in the blade outer region, which develops at the housing wall and is thick in the case of long inflow paths, causes unfavorable inflow conditions in the blade outer region if these are not compensated by a complicated blade geometry. A further disadvantage is the high outlay on production required because of the narrow clearances required between the housing and impeller.